Cytological changes in association with ethoxyresorufin O‐deethylase induction in fish upon dietary exposure to benzo[a]pyrene

Abstract

Juvenile areolated grouper (Epinephelus areolatus) were exposed to two levels of dietary benzo[a]pyrene (BaP; 0.25-12.5 microg/g body wt/d) for four weeks, followed by four weeks of depuration. Significant increase in hepatic ethoxyresorufin O-deethylase (EROD) activities was found after one week, preceding an increase in lipopigments (as measured by quantitative transmission electron microscopy) in week 2 of exposure. The EROD activities in the BaP-treated fish subsided at week 4 of exposure and throughout the depuration period. Lipopigments in the high-dose group appeared to be more persistent than that of the EROD activity during the exposure period and remained significantly higher than that of the controls at week 4. Levels of lipopigments, however, rapidly subsided on withdrawal of BaP exposure. These results appear to suggest that changes in EROD activities would precede cytological changes and that both the observed cytological and biochemical changes are reversible. Results of the present study also lend further support to our earlier findings on Solea ovata, that a significant relationship exists between EROD activity and lipopigment accumulation (as measured by volume density, absolute volume, numerical density, and absolute density; r = 0.483-0.358, p < 0.05), regardless of fish species (S. ovata and aerolated grouper) as well as the routes of exposure to BaP (intraperitoneal injection or dietary exposure). This provides strong supporting evidence that elevated EROD activities in fish liver do not merely indicate exposure to polyaromatic hydrocarbons (PAHs) but are also associated with significant biological effects. Our results showed that hepatic EROD activity and lipopigments could be used to indicate recent exposure of the fish to BaP/PAHs.